Plant cell (Brassica napus) response to europium(III) and uranium(VI) exposure

Henry Moll,Susanne Sachs,Gerhard Geipel

doi:10.1007/s11356-020-09525-2

Henry Moll, Susanne Sachs + Show 1 more

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https://doi.org/10.1007/s11356-020-09525-2

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Abstract

Experiments conducted over a period of 6 weeks using Brassica napus callus cells grown in vitro under Eu(III) or U(VI) stress showed that B. napus cells were able to bioassociate both potentially toxic metals (PTM), 628 nmol Eu/gfresh cells and 995 nmol U/gfresh cells. Most of the Eu(III) and U(VI) was found to be enriched in the cell wall fraction. Under high metal stress (200 μM), cells responded with reduced cell viability and growth. Subsequent speciation analyses using both metals as luminescence probes confirmed that B. napus callus cells provided multiple-binding environments for Eu(III) and U(VI). Moreover, two different inner-sphere Eu3+ species could be distinguished. For U(VI), a dominant binding by organic and/or inorganic phosphate groups of the plant biomass can be concluded.

Highlights

The transfer of radionuclides such as actinides through the environment represents a critical safety concern for both nuclear waste repositories and former uranium mining and milling sites that must be made secure
B. napus cells tolerated the low metal concentrations of 20 μM U(VI) and 30 μM Eu(III), with cell vitalities around 100% compared to the control samples; in contrast, a very significant decrease in the cell vitality was measured at 200 μM Eu(III) or U(VI) (Fig. 1c)
The 7F1 peak should not be influenced by complexation, for all our plant cell suspensions, we observed a slight decrease in intensity combined with a broadening of this transition

Summary

Introduction

The transfer of radionuclides such as actinides through the environment represents a critical safety concern for both nuclear waste repositories and former uranium mining and milling sites that must be made secure. PTMs can replace essential metal ions from their binding sites in enzymes, damage sulfhydrylgroup-containing proteins, accelerate the formation of reactive oxygen species, and trigger antioxidant defense mechanisms in plants (e.g., Weiler and Nover 2008; Serre et al 2019; Aranjuelo et al 2014). To overcome this unwanted chain of events, plants synthesize protective metal binding metabolites, store metal chelates in vacuoles or secrete them into the rhizosphere (Weiler and Nover 2008), and deposit defense polymers such as callose or lignin (Serre et al 2019)

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